Salazar Slytherin

According to the sorting hat, Slytherin hailed from the fen and had the gift of Parseltongue, enabling him to talk to snakes, same as Harry. As Dumbledore once said, Slytherin hand picked his students for "resourcefulness, determination ... and a certain disregard for rules."

Slytherin strongly believed that only true blooded witches and wizards had the right to go to Hogwarts, a view which brought him much opposition from Gryffindor and a view which, eventually, would drive him away from the school.

Slytherin built the chamber of secrets, unknown to his fellow founders. It contained a monster so fierce, it would finish his "noble purpose" of killing all the Muggle-born students at Hogwarts and could only be awakened by the true heir of Slytherin. This monster was a Basilisk, a suitable choice for a Parseltongue.